Method for Supporting Idle Mode in Wireless Local Area Network System

1. A method for supporting an idle mode of a terminal in a wireless local area network (WLAN) system, the method comprising: transmitting a first request message for starting an idle mode to a first access node to which the terminal is currently connected; receiving a first response message with respect to the first request message from the first access node; and starting an idle mode when the first response message includes acceptance information accepting a start of the idle mode, and rejecting the start of the idle mode when the terminal fails to meet predetermined conditions for starting the idle mode, wherein when the terminal moves to an area of a second access node while in the idle mode, the first access node recognizes that the terminal has moved upon receiving a request message for releasing resources allocated to the terminal transmitted by the second access node, and upon receiving the request message for releasing the resources, the first access node terminates supporting of the idle mode of the terminal and releases the resources allocated to the terminal, and wherein when the terminal initially moves to the area of the second access node, the terminal transmits a reassociation request message to the second access node, and the second access node transmits the request message for releasing the resources to the first access node by using information included in the reassociation request message.

2. The method of claim 1 , further comprising: receiving a paging indication message from the first access node in the idle mode; transmitting a second request message for terminating the idle mode to the first access node; receiving a second response message with respect to the second request message from the first access node; when the second response message comprises acceptance information regarding the termination of the idle mode, terminating the idle mode.

3. The method of claim 2 , wherein the paging indication message is received through at least one of a beacon message, a multicast/broadcast message, and a flexible multicast service (FMS).

4. The method of claim 2 , wherein the paging indication message comprises a terminal identifier identifying the terminal or a terminal group identifier identifying a group of the terminal.

5. The method of claim 1 , further comprising: when the terminal moves to an area of the second access node in the idle mode, the terminal transmits a third request message for a connection to the second access node to the second access node; and receiving a third response message with respect to the third request message from the second access node.

6. The method of claim 5 , wherein the third request message comprises a medium access control (MAC) address of the first access node.

7. The method of claim 6 , wherein, when there is traffic with respect to the terminal, the third response message further comprises paging information indicating termination of the idle mode of the terminal.

8. The method of claim 6 , further comprising, when there is traffic with respect to the terminal, receiving a paging indication message from the second access node after the third response message is received.

9. The method of claim 1 , further comprising receiving a paging indication message from the first access node, the paging indication message includes traffic arrival information and is transmitted by the first access node when traffic arrives from a network for the terminal that has started the idle mode.

10. A method for supporting an idle mode of a terminal in a WLAN system by an access node, the method comprising: receiving a request message for a connection to the access node from a terminal that has entered an area of the access node while operating in an idle mode; when it is determined that Internet protocol (IP) handoff is required for the terminal, transmitting an IP handoff request message to an IP handoff supporting device to which the access node is connected; and after the IP handoff supporting device performs an IP handoff procedure, establishing a connection with the terminal, based on information included in the IP handoff request message, wherein when the terminal enters the area of the access node while operating in the idle mode, an old access node recognizes that the terminal has moved based on a request message for releasing resources from the access node, and upon receiving the request message for releasing the resources, the old access node terminates supporting of the idle mode of the terminal and releases the resources allocated to the terminal, wherein when the terminal initially enters the area of the access node, the terminal transmits a reassociation request message to the access node, and the access node transmits the request message for releasing the resources to the old access node by using information included in the reassociation request message, and wherein the idle mode is initially started when a response message from the old access node includes acceptance information accepting a start of the idle mode, and is initially rejected when the terminal fails to meet predetermined conditions for starting the idle mode.

11. The method of claim 10 , wherein the IP handoff request message comprises at least one of a MAC address of the terminal, a MAC address of the old access node to which the terminal was previously connected, and an IP address of an old IP handoff supporting device to which the old access node was connected.

12. The method of claim 11 , wherein the access node obtains the MAC address of the terminal and the MAC address of the old access node from the request message.

13. The method of claim 10 , wherein the IP handoff supporting device maintains a table including IP addresses.

14. An Internet protocol (IP) handoff method of a terminal in a WLAN system, the method comprising: transmitting a request message for connection to an access node, to the access node, when the terminal enters an area of the access node while operating in an idle mode; receiving a response message with respect to the request message from the access node; receiving a router broadcast message regarding IP handoff from the access node; and performing IP handoff by using the router broadcast message, wherein when the terminal enters the area of the access node while operating in the idle mode, an old access node recognizes that the terminal has moved based on a request message for releasing resources from the access node, and upon receiving the request message for releasing the resources, the old access node terminates supporting of the idle mode of the terminal and releases the resources allocated to the terminal, wherein when the terminal initially enters the area of the access node, the terminal transmits a reassociation request message to the access node, and the access node transmits the request message for releasing the resources to the old access node by using information included in the reassociation request message, and wherein the idle mode is initially started when a response message from the old access node includes acceptance information accepting a start of the idle mode, and is initially rejected when the terminal fails to meet predetermined conditions for starting the idle mode.

15. The method of claim 14 , wherein the request message comprises information requesting that the access node converts a multicast message or a broadcast message into a unicast message and transmits the converted unicast message.

16. The method of claim 15 , wherein the response message comprises acceptance information with respect to the information requesting the conversion into the unicast message and transmission of the converted unicast message, and when receiving the router broadcast message, the router broadcast message is received as a unicast message.

17. The method of claim 15 , wherein the request message further comprises a MAC address of the terminal and a MAC address of the old access node to which the terminal was previously connected.

18. A method for supporting, by an access node, IP handoff of a terminal in a WLAN system, the method comprising: receiving a request message for a connection to the access node from a terminal that has entered an area of the access node while the terminal is operating in an idle mode; transmitting a response message with respect to the request, to the terminal; transmitting a router broadcast message regarding Internet protocol (IP) handoff in a unicast manner to the terminal; and performing IP handoff by the terminal, using the router broadcast message, wherein when the terminal enters the area of the access node while operating in the idle mode, an old access node recognizes that the terminal has moved based on a request message for releasing resources from the access node, and upon receiving the request message for releasing the resources, the old access node terminates supporting of the idle mode of the terminal and releases the resources allocated to the terminal, wherein when the terminal initially enters the area of the access node, the terminal transmits a reassociation request message to the access node, and the access node transmits the request message for releasing the resources to the old access node by using information included in the reassociation request message, and wherein the idle mode is initially started when a response message from the old access node includes acceptance information accepting a start of the idle mode, and is initially rejected when the terminal fails to meet predetermined conditions for starting the idle mode.

19. The method of claim 18 , wherein the request message comprises information requesting that the access node converts a multicast message or a broadcast message into a unicast message and transmits the converted unicast message, and the response message comprises acceptance information with respect to the information requesting the conversion into the unicast message and transmission of the unicast message.

20. The method of claim 18 , wherein the access node receives the router broadcast message from a network and previously stores the received router broadcast message.